Field of the Invention
The present invention relates to a thin-film piezoelectric material element which has a piezoelectric material and electrodes having thin-film like shape, head gimbal assembly and hard disk drive having the thin-film piezoelectric material element.
Related Background Art
A hard disk drive has a large recording capacity and is used as the heart of a storage device. The hard disk drive records and reproduces data to/from a hard disk (recording medium) by a thin-film magnetic head. A part, which the thin-film magnetic head is formed, is called as a head slider, and a part, which the head slider is mounted on the edge part, is a head gimbal assembly (will also be referred to as HGA).
Further, recording and reproducing of data to/from the recording medium is performed by flying the head slider from a surface of the recording medium while rotating the recording medium, in the hard disk drive.
On the other hand, it has become difficult to control a position of the thin-film magnetic head accurately by control with only a voice coil motor (VCM), because heightening a recording density of the recording medium has developed in company with increase of a capacity of the hard disk drive. Therefore formerly, a technology, which an actuator having supplementary function (a supplementary actuator) is mounted on the HGA in addition to a main actuator with the VCM, and the supplementary actuator controls a minute position that is not able to be controlled by the VCM, is known.
A technology, which the main actuator and the supplementary actuator control the position of the thin-film magnetic head, is also called two stage actuator system (dual-stage system).
In the two stage actuator system, the main actuator makes drive arms rotate to decide a position of the head slider on a specific track of the recording medium. Further, the supplementary actuator adjusts the position of the head slider minutely so that the position of the thin-film magnetic head may become an optimum position.
A micro actuator using a thin-film piezoelectric material element is known formerly as the supplementary actuator. The thin-film piezoelectric material element has a piezoelectric material and a pair of electrodes formed to sandwich the piezoelectric material, and each of them is formed to be a thin-film shape.
Further, a technology, which displacement stroke of the element is increased to increase the displacement control amount of the magnetic head, is conventionally known (for example, see U.S. Pat. No. 8,885,294 (referred also to as Patent Document 1)). The HGA having a following structure is disclosed in the patent document 1. The HGA has the structure which the piezoelectric material element is fixed to the bottom of concave part formed on a gimbal part. It is possible to prevent the stroke of expansion or shrinking of the thin-film piezoelectric material element from escaping in a curved direction, thereby the displacement stroke of thin-film piezoelectric material element increase.
On the other hand, to avoid electrical shorting between the upper electrode film and the lower electrode film, the piezoelectric material element, which the insulating layer made of oxide or poly-imide are formed to wrap on the top surface and side surfaces of four direction of piezoelectric material, is known (for example, see U.S. Pat. No. 6,931,700 (referred to also as Patent Document 2), U.S. Pat. No. 7,006,334 (referred to also as Patent Document 3)). An opening of the insulating layer is formed on the top surface of the piezoelectric material so that the top surface of the piezoelectric material is exposed, in these thin-film piezoelectric material elements. Further, the HGA, having a flexure including a structure with the piezoelectric element, is disclosed in JP 2014-106985 (referred to also as Patent Document 4). The thin-film piezoelectric material element is fixed to the flexure, in the HGA.